Unwind reel control



Oct. 25, 1949. M. MICHEL UNWIND REEL CONTROL Filed July 31, 1948 Q WW 3AW 7/ 1 3 w: m m M w \m I; Q\I 2 Patented Oct. 25, 1949 UNITED STATESPATENT OFFICE UNWIND REEL CONTROL Mathias Michel, Pittsburgh, Pa.

Application July 31, 1948, Serial No. 41,787

This invention relates to control systems for unwind reels adapted tounwind strip material under tension as it is fed to a strip processingmachine, such as a rolling mill, trimmer, slitter, leveler, or the like.The term strip is used generally, as the invention is applicable tounwind reel controls for wide or narrow strip, band, wire or other formsof material unwound in long lengths from reels.

It is recognized that it is desirable to main-' tain strip, unwindingfrom a coil on a reel to a strip processing machine, under asubstantially constant tension regardless of changes in processing speedor changes in coil diameter (with consequent changes in speed ofrotation of the coil and reel). Mechanical devices for restraining therotation of unwind reels are inherently sluggish in operation, if notincapable of properly controlling the tension developed in the unwindingstrip. Electrical controls for this purpose have been developed to ahigh degree of accuracy, but are usually expensive to install and/or tomaintain.

One object f this invention is to provide an inexpensive electricalunwind reel control capable of ready adjustment for the maintenance ofsubstantially constant selected values of tension on strip material fedfrom the unwind reel. The control system of the invention is simple andefficient, and yet it is highly accurate in operation. It is also anobject of the invention to avoid the use of current and voltageregulators of the contact or vibrating contact type, since they requireconsiderable maintenance.

Other objects and advantages of the invention will become apparent upona reading of the following detailed description of a preferredembodiment of the invention, which description has reference to the twofigures of the accompanying drawing.

Figure 1 shows a mechanical arrangement of the various elements of theinvention. Figure 2 is a schematic diagram of the electricalconnections.

Fig. 1 shows, by way of example, a mechanical arrangement of the variousinstrumentalities for the application of the unwind control system to arolling mill. In this figure an unwind reel I is shown supporting a coilII from which strip material l2-is fed to a rolling mill l5. The unwindreel I0 is coupled, through suitable shafts, couplings and gears, to adirect current drag generator 20. The rolling mill I5 is coupled,through suitable couplings, spindles, pinions, and gears to a main millmotor 25. To the main mill motor 25, a direct current feed-back motor 35is suitably coupled; and to the feed-back motor. 35. a direct currentcontrol exciter 45 is suitably coupled. Feed-back motors 35 and controlexciter 45 may, however, be separately operated at speeds pro- 5 Claims.(Cl. 242-75) 2 portional to the mill speed, without being coupleddirectly or indirectly thereto.

The arrangement of motor, exciter, and genera or with the unwind reeland mill, as shown in Fig. 1, permits the following mode of operation.Mill motor 25 drives rolling mill l5 which pulls the strip |2 off coilheld on unwind reel It), thus imparting rotation to unwind reel III(which drives drag generator 20) and creating tension in the strip l2.The power developed by drag generator 20 is delivered to feed-back motor25 Which can take some of the load of driving mill I5. Control exciter45 is electrically associated with drag generator 20 in a manner whichwill be explained by reference to Fig. 2.

Fig. 2 shows the electrical arrangement of the motors, exciter, andgenerator shown in Fig. 1. It will be noted from this figure that draggenerator 20 and feed-back motor 35 have their armatures connected inloop circuit by lines l3 and H. A booster generator l6 may be insertedin this loop circuit, for a purpose to be referred to later, but it isnot essential that it be employed. A contact switch I! is alsopreferably provided in this loop circuit. The feed-back motor 35 ispreferably series wound, being provided with a series-field 36.

The drag generator 20 is provided with a control field 2|. One side ofcontrol field 2| is con nected through a portion of line |3 with onearmature terminal of drag generator 20; the other side of control field2| is connected with that armature terminal of control exciter 4 5 whichis of polarity corresponding to that of the armature terminal of draggenerator 20 to which the firstmentioned side of control field 2| isconnected as above-described. The other armature terminal of controlexciter 45 is connected through a portion of line l4 with the secondarmature terminal of drag generator 2|l, these terminals also being ofcorresponding polarity.

The control exciter 45 is preferably provided with a series field 4G,and has a separatel excited shunt field 41.

The shunt field 41 is controlled by a rheostat 48. The drag generator.is also preferably provided with a separately excited shunt field 22,which may be controlled by a rheostat 23. Rheostats 48 and 23 may be soarranged as to be commonly adjusted by a single rheostat shaft, asshown.

The unwind control system functions as follows: The separately excitedshunt field 22 for drag generator 20 is given a fixed excitation for agiven tension condition by adjustment of rheostat 23. Likewise, theseparately excited. shunt field 41 for control exciter 45 is given afixed excitation by adjustment of rheostat 48. Control exciter 45-.

will develop a potential on control field 2| generall proportional tothe speed of the strip |2 passing through the mill l5, while draggeneraassays? tor 20 will tend to develop a potential proportional tothe speed of rotation of the unwind reel iii. If a higher potential isdeveloped across the armature of drag generator 20 than across thearmature or control exciter 45, then current will flow through thecontrol field 2i, opposing shunt field 22 and reducing the excitation ofdrag generator 20. Contrarily, ii a lower potential is developed by draggenerator 20 than by the control exciter 45, then current will flowthrough the control field 2| in an opposite direction, increasing theexcitation of drag generator 20. The system tends to keep the samevoltage on drag generator 20 as is developed by control exciter 45,regardless of the speed of unwind reel i and the corresponding speed ofdrag generator 20. Since control exciter 45 is driven at a speedproportional to the speed of the strip l2, then for a given externalexcitation thereof determined by the setting of rheostat 48, itspotential is always proportional to strip speed. Likewise, the potentialon drag generator is proportional to strip speed and not unwind speed.Thus tension can be maintained at a substantially constant selectedvalue on strip ii.

The series field 46 for the control exciter 45 reduces the output ofcontrol exciter 45 where current flows through its armature in order tocompensate for the IR drop in the control field 2i oi. drag generator 20and in the armature of control exciter 45, so as to maintain as nearlyconstant potential on drag generator 20 as possible when the controlsystem is operating.

The booster generator I 6 supplies added potential to compensate for theIR drop in the loop circuit containing drag generator 20 and feed-backmotor 35, and can be regulated for different amounts of compensatingeffect in accordance with requirements of the system.

Rheostats 48 and 23 can be commonly adjusted to establish a new value ofstrip tension, since they permit new values of excitation of draggenerator 20 and control exciter 45 to be established.

to maintain substantially constant tension on strip material redtherefrom to a driven process-' ing machine comprising a drag generatordriven by the unwind reel, a feed-back motor arranged to be operated ata speed proportional to that of the driven processing machine, said draggenerator and said feed-back motor having their armatures connected inloop circuit, a control exciter.

for said drag generator driven at a speed proportional to that of thedriven processing machine, and a control field for said drag generator,said control exciter having its armature terminals connected, in serieswith said control field, across the armature terminals of correspondingpolarity of said drag generator.

2. A control system for an unwind reel adapted to maintain substantiallyconstant tension on strip 4 material fed therefrom to a drivenprocessing machine comprising a drag generator driven by the unwindreel, a feed-back motor arranged to be operated at a speed proportionalto that of the driven processing machine, said drag generator and saidfeed-back motor having their armatures connected in loop circuit, aseparately excited shunt field for said drag generator, a controlexciter for said drag generator driven at a speed proportional to thatof the driven processing machine, and a control field for said draggenerator, said control exciter having its armature terminals connected,in series with said control field, across the armature terminals ofcorresponding polarity of said drag generator.

3. A control system for an unwind reel adapted to maintain substantiallyconstant tension on strip material fed therefrom to a driven processingmachine comprising a drag generator driven by the unwind reel, afeed-back motor arranged to be operated at a speed proportional to thatof the driven processing machine, said drag generator and said feed-backmotor having their armatures connected in loop circuit, a separatelyexcited shunt field for said drag generator, a control exciter for saiddrag generator driven at a speed proportional to that of the drivenprocessing machine having aseparately excited shunt field and a seriesfield in its armature circuit, and a control field-for said draggenerator, said control exciter havingits armature terminals connected,in series with said control field, across the ,armature terminals ofcorresponding polarity 01 said drag generator.

4. A control system for an unwind reel adapted to maintain substantiallyconstant tension on strip material fed therefrom to a driven processingmachine comprising a drag generator driven by the unwind reel, afeed-back motor arranged to be operated at a speed proportional to thatof the driven processing machine, said drag generatorand said feed-backmotor having their armatures' connected in loop circuit, a boostergenerator in said loop circuit, a control exciter for said draggenerator driven at a speed proportional to that of the drivenprocessing machine, and a control field for said drag generator, saidcontrol exciter having its armature terminals connected, in series withsaid control field, across the armature terminals of correspondingpolarity of said drag generator.

5.,--A control system for an unwind reel adapted to maintainsubstantially constant selected valves of tension on strip material fedtherefrom to a driven strip processing machine such as a motor drivenrolling mill comprising a direct current drag generator coupled to theunwind reel, 8. direct current series wound feed-back motor 'coupled tothe driven strip processing machine,

No references cited.

